The invention relates to a warning signal control system for motor vehicles.
A warning signal control system for motor vehicles is known by way of example from German Utility Model Specification DE 203 02 083 U1. This warning signal control system combines the normal audible horn with the headlight flasher by means of a common steering wheel switch as an operator control element provided specifically for that purpose.
It is an object of the invention to configure an apparatus of the type cited at the outset to be more situation-adaptive.
This and other objects are achieved by a warning signal control system according to the invention equipped with a visual warning signal actuator, preferably what is known as the headlight flasher, which is present anyway, and with an audible warning signal actuator for outputting a vehicle-external warning sound that is different than the normal horn signal. Additionally, at least one electronic control unit and a single operator control switch are provided, the switching signal of which operator control switch is an input signal for the control unit and by which operator control switch both the visual warning signal actuator and the audible warning signal actuator are separately or collectively activable. In this case, operation of the operator control switch prompts activation of the visual warning signal actuator and/or of the audible warning signal actuator to be controllable at least on the basis of the vehicle speed.
The operator control switch is preferably the operator control element that is also provided for the normal headlight flasher function anyway, and is used by the invention in a multifunctional manner.
The following warning sounds can preferably be used:                an audible standard signal for particularly quiet road users (e.g. electric vehicles), for example prescribed by a standards setting body in the future,        a horn signal that is different than the normal horn signal at least by virtue of reduced volume,        an audible signal similar to a bicycle bell, or        an audible signal that is also used to output a warning sound when reverse gear is selected.        
The invention is based on the following insights.
Road users, particularly cyclists and pedestrians, also detect vehicles by virtue of the sound of internal combustion engines. If this sound is not present (e.g. in the case of electric vehicles), a hazard can arise. An additional continuous sound generated by a sound generator would provide a remedy to the hazard to vehicle-external road users, but is unwanted for reasons of noise pollution.
Operation of the combining dual warning signal switch in the steering wheel according to the aforementioned prior art results in considerable noise pollution, particularly in city operation. In a dangerous situation, the driver is also overtaxed by the decision concerning which operator control element he is then meant to choose in order to output a warning signal. The selection would then involve three switches, namely the switch associated with the normal audible horn in the center of the steering wheel, the operator control lever switch associated with the normal headlight flasher next to the steering wheel and an additional steering wheel switch, associated with the combination of both warning signals, in accordance with German Utility Model Specification DE 203 02 083 U1.
An advantageous alternative in this regard is a warning sound activable by the driver depending on the situation. This sound is not intended to be the “horn”, but rather is meant to be a quieter and more pleasant sound (e.g. similar to a bicycle bell or an audible standard signal that may be prescribed in the future for electric vehicles or other particularly quiet road users). There is also not yet a standard operator control element available for activating such a warning sound.
The operator control element must be usable intuitively and quickly. Since the hands should remain on the steering wheel in a situation that necessitates warning road users, an operator control element is needed on the steering wheel.
Optimum operator control on the basis of size and locatability can be found, on the basis of the empirical insights of the inventor, only on the steering column levers or in the region of the shift paddles.
It is already generally known practice to provide the motor vehicle driver with a visual warning signal for road users by virtue of operation of what is known as the headlight flasher (pulling the left-hand steering column lever).
The invention makes use of this circumstance. The additional warning sound is preferably switched on in addition to the activation of the headlight flasher, particularly when the steering column lever is operated, for as long as the lever is pulled.
Activation of the warning sound is performed on the basis of the vehicle speed, however, in order to prevent unnecessary noise pollution. By way of example, above a particular speed threshold (e.g. 60 km/h or the particular current maximum permissible speed in cities, for example detectable by means of road sign recognition or a navigation system), only the headlight flasher is activated when the steering column lever is operated. Below the speed threshold, either both warning signals or only the audible warning sound is/are output. The warning sound could also be output either alone or together with the headlight flasher in a particular lower speed range above standstill. In that case, at a standstill or a very low speed—that is to say when the danger potential is very low—, it would again be possible to operate only the headlight flasher in order to reduce noise.
The invention results in the advantages of intuitive and fast operator control in critical traffic situations. Furthermore, no additional operator control elements are needed.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.